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Jackie O writes "According to an employee blog on the Liftport Group website, their prototype robot for the Space Elevator has just successfully climbed a 260-foot building (in a driving snowstorm, no less) at MIT. Now all they have to get it to do is climb over 60 thousand miles into space, carrying things. Good luck there."Update: 11/17 05:17 GMT by T: Liftport has posted some photos from the ascent, too. Thanks!

Ah, collegiate rivalry. While some refer to Caltech as the MIT of the West, on the campus tour they tell you that MIT is actually the Caltech of the East. This always gets a laugh, particularly among those who know that MIT was founded in 1861 and Caltech was founded in 1891 (as an arts & crafts school, oddly enough).

It's a good idea in theory, but there's the small problem of someone has to go to the top of the building/object to anchor the ribbon in the first place. So once they work around that, it should be fine.

And the fact that a rope and pully would do the same job faster just occured to me.

It's a good idea in theory, but there's the small problem of someone has to go to the top of the building/object to anchor the ribbon in the first place. So once they work around that, it should be fine.

And the fact that a rope and pully would do the same job faster just occured to me.

I don't know if it is even a good idea in theory. Velocity differences and rotations between the two anchoring points would need to be considered. Even if one was going to try to use a geostationary satellite as one end-p

Yeah...this is slashdot so ignorance is acceptable. Let me quickly explain how a space elevator is supposed to work.

An EXTREMELY strong tether is fixed to a large mass far out in orbit, this mass along with the earth's rotation hold the tether very taut and allows for smaller masses to scale up it. Much like if you tied a small weight to a string and whirled it around your head, imagine a small robot climbing the string...thats the idea of a space elevator.

The issue with the idea of a space elevator currently is the technology that would go into the tether. It is believed that many strands of carbon nano tubes, those tiny super strong tubes grown/created long and attached together, would be able to withstand the stress.

Next the tether would not be round like a rope, but flat like a belt. Being flat, it would be much harder to get twisted if sufficient force is applied to each end, pulling the ends apart.

I did a lot of calculations about this a few years back; here are some results that might interest you. Here's the apparent strength of gravity as you go up the elevator, allowing for both the earth's rotation and the 1/r field:

Weightlessness comes at the Clarke point, of course, 35950 km up. Above that, there is a centrifugal effect, and the earth appears to be 'above' you---but you would have to be nearly 200,000 km up before the apparent gravity reaches -1.0 m/s. In practice, no one would build it out that far; you just want to go far enough to keep the center of gravity at the Clarke point, plus a bit more to put the lower end of the elevator in tension. A big mass just slightly above synchronous orbit is probably the way to go.

Midway Station, the lowest point where you go into an elliptical orbit instead of hitting the ground if you jump off, is 23450 km up, and has a tiny apparent gravity of 0.29 m/s. The total energy cost from ground to the Clarke point is just over 13 kW-hr per kg lifted, which means $100 a ticket at today's energy prices, minus savings for energy generated by the 'down' cars, plus (rather large) financing charges on the capital investment.

Next come strength-of-materials considerations. We need a material with the highest possible (breaking strength)/(density), which is a tough sell, because Kevlar, good piano wire, and nearly everything else has essentially the same optimum value for this parameter. They all have breaking strengths of a 'few' billion Pa, and a density of a 'few' thousand kg/m, where 'few' is the same number in both cases. The strongest high-tensile materials are the heaviest, by and large. Exotic materials like spun sapphire or diamond do better on the micron scale, and buckytubes get close to the theoretical limit (the strength of the chemical bonds themselves). In principle, such materials should be anywhere from 40 to 120 times stronger than the optimal value above, which I shall call '1x piano wire'. But Griffith theory teaches us that the length of the 'critical' crack (one that releases enough energy to drive its own spontaneous propagation) goes down as 1/(stress). So even if exotic materials can be machined in gigaton lots, we may find that they are unusable at the huge stresses we need. The first woodpecker that comes along may bring the whole thing down if the critical crack is a few microns long.

But let's assume we can cope with this issue, if necessary with nanobot inspectors checking for micro-cracks, or simply a sheath of unstressed material around the structural members. The tension is essentially zero at the bottom: if we wanted we could leave the cable hanging loose a foot from the ground. (We want some tension there, of course, when we build an actual elevator, or the dynamic oscillations will kill us.) At the Clarke point, where the stress is largest, the stress depends on the weight of the tower below, which depends on the strength of the material. It's like rocketry, ironically enough: the 'fuel' for the upper stages is 'payload' cost for the lower ones. In this case, of course, it's upside-down: we have to keep the lower part of the tower as light as we dare, so that the upper part doesn't have to be exponentially heavy. And a high-tensile steel tower, like a rocket powered by Wisconsin butter (happy now, Senator Proxmire?), just doesn't have enough juice.

Assuming each wire has to take a thousand tonnes of tension at the bottom (add wires as needed, depending on what you want to send up the tower...), we get a minimum thickness profile like this:

But Griffith theory teaches us that the length of the 'critical' crack (one that releases enough energy to drive its own spontaneous propagation) goes down as 1/(stress). So even if exotic materials can be machined in gigaton lots, we may find that they are unusable at the huge stresses we need. The first woodpecker that comes along may bring the whole thing down if the critical crack is a few microns long.

I don't think this has to be a dealbreaker. If carbon nanotubes are used, their natural structural

In 1980 (79?) I did a Co-op block at Comsat, the US part of Intelsat, responsible for the first telecommunications satelites. Because these were first described by Arthur Clarke in a science fiction story, he was given the 'first' share of stock in the company and began a long and friendly relationship with the people there. Fast forward to my tenure, where I was working with the 'resident genius' in my department (I don't know what his actual title was, but essentially he had no formal assignments other than to come up with amazing things) using some god-awful quasi-language based on fortran (it was supposed to be really good at matrix calculations and I was writing a program to calculate solar cell array degradation over the life of a satelite. It was my first introduction to dealing with something billed as 'amazing' that almost, but not quite, did what you needed it to do. But I digress from this digression...). I would frequently see him pouring over calculations and eventually asked him what he was doing. "Calculating the tensile strength needed to make a space cable." Then followed a lengthy discussion of what we now call a space elevator. I asked if Comsat was planning to build one. It turns out Arthur Clarke had asked him to do the calculations for a book he was currently writing. I assume his genesis of the idea led to it being called the Clarke point.

I never actually read the book, as, although I always find Clarke's ideas interesting, his writing just grates on my nerves.

these were first described by Arthur Clarke in a science fiction story

Actually, I believe it was an essay or an editorial. It was published in "Wireless World", a British electronics magazine. AFAIK, Clarke patented the geostationary orbit, but his patent expired before anyone had the capacity to put a satellite there.

Arthur Clarke had asked him to do the calculations for a book he was currently writing

The book was "Fountains of Paradise", where a space elevator was built in an island located south of

It's a good idea in theory, but there's the small problem of someone has to go to the top of the building/object to anchor the ribbon in the first place.

Hot-air balloons (manned or unmanned) should do the trick for the next generation or two of the technology. After that, intermediate (~1000km) lengths could be tested by tethering two satellites together and letting tidal forces pull the ribbon taut.

Then comes the real Space Elevator, and after that, once we get cocky, we can try lowering an Elevator

It's 60 miles to the beginning of space, and approximately 20,000 miles to geosynchronous orbit. The anchor for the space elevator needs to be at 3x geosynchronous orbit or approximately 60,000 miles out. They had that number right, but your comment emphasizes the Herculean nature of the task.

Woohoo! I have to say that the creator of our robotic lifter, David Shoemaker, rocks! The latest incarnation of the lifter faced what was probably its most difficult challenge to date: climb MIT's 290-foot-tall Green building in the middle of driving snow. And the robot succeeded marvelously, despite some problems!

The morning started off cool, but with temperatures dropping. Blaise Gassend and I brought everything for the rooftop anchor station up to the roof and got it assembled. There was a bit of ice rain that started falling (and melting once it landed), but it wasn't too bad. Once the anchor station was assembled, we headed back inside to finish prepping the ribbon and to work on insulating the lifter's battery. When we went back outside, the weather had changed - it was now a very serious snow storm! I decided that we could go ahead with the lifter test, since the wind wasn't too bad, and I thought that snow was at least better than rain.

We had planned on attaching a safety line to the robot to catch it in case the ribbon broke (which we weren't expecting, but we wanted to be extra cautious). Unfortunately, the safety line was a last minuted addition that did not get tested in advance, and of course it was the thing that broke. Partway up the ribbon, the string that was hooked to the safety rope got tangled in the axle of the lifter, and the rope itself was separated from the string. So our safety line turned out to be more of a detriment than a help! And due to the wind, the ribbon got twisted around perhaps 10 whole revolutions, which also slowed the lifter's ascent. But the lifter kept going, and even though it was slower than normal, it made it all the way up to the roof level, reversed course and headed back down (halfway up, the twist in the ribbon unwound itself).

I want to thank Blaise Gassend for his great help in setting things up and preparing part of the ribbon. Look for pictures and perhaps video to be online within the next few days, and perhaps a more detailed description of the event.!

Every time this is mentioned, I get all kinds of Larry Niven RingWorld flashbacks for some reason.

As cool as this idea is, there are some problems (especially for the lower altitudes). Some of the problems are more serious than others:

Wind shear: winds at various altitudes can differ widely. Both the cable and anything climbing it will be affected.

Resonance: a cable will tend to vibrate; it will be necessary to dampen the vibration. Usually this is done with strategically placed weights. With an object climbing the cable, however, the resonance will be constantly changing.

No Adspace: There will be no place to put banner ads, so the thing will never be profitable [slashdot.org].

Environmentally Harmful: birds could run into it and die. Doesn't anyone consider birds?

I tend to think more of Kim Stanley Robinson's Mars series - since the space elevator is key in them, whereas I can't remember a single elevator in the Ringworld books.

In the Mars series, these points are largely addressed. Wind shear and resonance are handled by thrusters placed every so often along the cable, managed by a supercomputer. Adspace isn't needed - the thing pays for itself because it's a transport mechanism. Mars has no birds.;)

In addition, he also brings up the issue of terrorism (those same locations that have thrusters also have anti-missile defenses), and the massive destruction the entire thing causes when it comes down, after they break off the counterweight asteroid it's using.

Terrorism: A space elevator is vulnerable to terrorism at every part of its length. A terrorist can target any section of the elevator, but we have to defend all of it. That's not a winning stragegy -- we have to take the fight to them.

So screw colonizing Mars, we need to occupy it now or the terrorists will win.

Yeah yeah, every space elevator story brings up the same old objections... they are all resolvable. The only really intractable problem will be convincing the religious right that this is not another "Tower of Babel" and therefore not sinful/doomed/evil/etc.

Actually since the ribbon doesn't need to support as much tension at atmospheric altitudes (as compared to at geosync) you can probably make it a lot narrower without making it much thicker. The main reason for width at that altitude will be to have enough surface area to provide friction/traction to support the climb.

I doubt you need to worry too much about resonance. The atmosphere can only apply forces over at most a few kilometers, a very small fraction of the ribbon's 40+Mm length, so you're extremely

Arthur C. Clark -- the guy who invented the idea of the geosync satellite -- said of the space elevator not too long ago, that "Itll be built 10 years after everybody stops laughing and I think they have stopped laughing." Here's to hoping that exponential progress [kurzweilai.net] in molecular nanotech makes his estimate a not-so-idealistic one.

I can't help but think about all the political hurdles that'll delay the space elevator more than any technical setbacks. And then I get to thinking about how slow and unromantic a space elevator ascent would be compared to the exciting phallic-rocket launch. Still, the space elevator is about the only way to eventually get launch costs below a dollar per pound; chemical rockets are too energy-wasteful to ever reach that point.

I know everybody's counting on exponential growth of nanotube-strength structures, but right now the longest nanotubes with the required strength are millimeters long. I once heard on Slashdot, "Once you can build a 40,000 millimeter bridge across a stream on campus, then we can start discussing a cable 40,000 kilometers long."

So I'll take that as my starting point. I'll stop laughing when I see that 40 meter horizontal bridge, that's still five orders of magnit

Heh, you're not going to run your ribbon climber with gasoline; you would have to haul oxidant with the gas for everything but the first few km.

If you have a space elevator, then you can start building Solar Power Satellites for pretty cheap. Anchor one to the end of the elevator and beam down the power with a laser to a receptor on your climber. So yeah, you'll pay $135/lb (already > 1 order of magnitude better than current launch prices) for the first SPS and you'll pay a lot less thereafter. Even at

I fail to see how climbing a 290 foot ribbon, on battery power, is even relevant to building a space elevator. It's realy just someone's fun little robotics engineering project. The amount of energy needed to climb all the way to space is so huge that either a highly energy dense storage medium not yet available, wireless power transmission, or transmitting power on the ribbons themselves if that turns out to be possible, are the only viable options to power a space elevator. Other than that, the lifter is a simple engineering project that could be built today.

Yeah, but just wait until some athlete climbs the space elevator... imagine: a contraption similar to those hand driven railway cars attached to the ribbon. The dude (or gal!) stops at 10,000 feet for Oxygen. Then again for a pressure suit and finally a space suit. Sure, it may take a while, but it's totally possible!

But I am going to refrain from getting excited until I see some serious work go into the cable structure. I imagine getting one of those to be strong enough and stable enough would be orders of magnitude more difficult than getting somthing to climb it once we do.

Power will be beamed to the lifters by a medium intensity near-infrared laser. It would not be a good idea to stand infront of such a laser, but it won't hurt you to run your hand through it or even to walk (or fly) quickly through it. The lifters will carry an array of photovoltaic cells keyed to the wavelength of the laser, making a surprisingly efficient power transfer.
The adaptive optics (for aiming and mitigating atmospheric distortion) and lasers themselves are in the demonstration stages (for other projects).

When article mentions driving snowstorm, this does actually mean a driving snowstorm with lots of snow and cold and wind and more snow and everybody trying to stay inside?

Or does it mean that it was fairly windy, snowing abit and it totalling a couple of centimeters on the ground and people who had watched to many catastroph-movies lately bandied about in Libraries burning books and being faintly surprised about how little warmth it produced?

They're making this sound like it's a step towards achieving their goal, but really what they did today wasn't a stretch of the imagination like the final goal is.

If I claimed that I can jump to the Moon, you'd look at me like I was crazy, because the laws of physics would be completely in opposition to my claim (for example bones would shatter long before you could exert the force to jump even 50 feet). Now if I showed you that I could jump 3 feet, would that really convince you that I'm making progress towards my claim of jumping to the Moon?

To get back to this space elevator idea, climbing 260 feet is no big deal at all using cables that we have today. It's simple work. However, making a cable that is 30,000+ miles and able to support its own weight plus the weight of the payload is impossible with these cables. They'd need a material that doesn't yet exist.

The real hurdle in this project is not making the robot climb the short conventional cables that are readily available, the real hurdle is getting a hold of cables of unbelievable strength made of a substance that doesn't yet exist.

Yes, if you showed me that after 6+ billion years of evolution you were capable of jumping 3 feet, and comprehending that you needed to jump more to reach the moon, then I would say you were making progress.

If that same robot could climb the full distance to a Lagrange point, and all we were now waiting for was the carbon fibre nano-tubes, would you say we'd made progress?

SO they are at the 'Kitty Hawk' stage of development. I mean, the Wright Brothers didn't really achieve too much and at the time no one thought too much of it seeing as how all they did was to fly for a few seconds really...

300 Gpa is the upper end of the theoretical spectrum. The best steels (and I mean ~the best~) are as much as 85+% of the max theoretical strength of steel. When carbon nanotubes reach 33% of their theoretical strength, we WILL build a Space Elevator. Let's collectively cheer on the researchers. If even 1/50th of the max strength is achieved, the world will change. Why aim to make bridges and elevators a little longer, or your tennis racket a little lighter? Let's aim for the big prize, the breakthrough, and grab the enhancements and improvements along the way.

Wow, I wasn't expecting my blog post to get/.'d. I was dead tired from the day of the test, and just wanted to get some info online for anyone who was curious. Sorry for not getting more details or photos up sooner.

BTW, the height of the building our robot climbed is 290 feet, not 260. Not a huge difference, but I wanted to correct the error in the original/. post.

After seeing more than a half-dozen comments on my blog post right after being slashdotted tonight, I got real motivated to get the pictures up ASAP. You can now see pictures of the day at http://www.liftport.com/gallery/MITdemo_2004Nov [liftport.com]

While this was perhaps a decent accomplishment, you shouldn't try to milk it with respect to the weather. While it did snow, it was only barely heavy enough for there to actually be snow the next day, and it was barely below freezing. In fact, the snow was alternating between snow and sleetish rainy cold annoying preccipitation.

So mad props, but if we were at the same MIT, the weather didn't really figure into the accomplishment:-)

Of course, had there been heavy winds, and there weren't, then you could

Yea, the snow wasn't bad at all. Just had to kick a little off my car. I drove in it, walked around in it, and the guy i work with went biking in it. No Biggie... and i figure the space elevator better work in the cold if it's gonna go up high..

I am sorry if this is a stupid question, but, what is the ribbon made out of? I know there has been much talk about carbon nanotubes being used for the ribbon material in the real deal. I guess where I am really going with this is, what is the signifigance of this goal? I am not trying to downplay any part of what you have done, I just simply don't know enough about the project as it stands today.

Or, slightly more verbosely, we can't build a space elevator because we can't construct a strong enough "ribbon". Carbon nanotubes are theoretically strong enough, but nobody has yet reported a macroscopic piece of material made from them that has the required tensile strength. While there is a lot of nanotube research going on, there's no guarantee that the right materials will be available soon. There's no guarantee that such materials will ever be available.

Don't get me wrong, I sincerely hope that the space elevator can be built. But until I can hold, in my hand, the requisite bit of unobtanium with enough tensile strength, I'll stifle my excitement.

You're right. The material we need has not been made yet. This is a barrier that can be broken. 105 years ago, heavier than air flight was impossible. Today, space flight is possible. 50 years ago, 1 kilobyte was huge (and on punch cards. Today 1 gigabyte is small.
We sometimes sound over zealous (I'll be the second to admit), but this is just a technical problem to solve. Better minds than mine are working on it right now.

Don't get me wrong, a space-elevator would be cool. But what's exciting about this work?

They made a robot climb a 290-foot strap. Big deal. They didn't have to worry about whether the strap would even support it's own weight (when you're talking about 60 miles, that's a tough engineering challenge), they didn't have to worry about the top end coming out of oribtal sync with the first end, they didn't have to worry about lightning strikes, and the list goes on.

This experiement is interesting, but unfortunately it does not help too much toward a space-elevator. Probably not a single part or technique from this climber can be used on a space-elevator climber. For example:

This one gets energy from a battery-stack. A battery-stack will not have enough energy to climb 36000 km to geostationary orbit. Infact current batteries are atleast 2 orders of magnitude too weak for that.

Climbing-mechanism is here based on gripping the ribbon. Thing is, climbing to geosynch is a 36000 km travel straigth up, even if a 36 hour climb-time is acceptable you'll need to climb at 1000km/h gripping this (or similar) gripping-mechanisms are not up to that, infact this thing climbs 3 orders of magnitude slower.

So, it has a energy-storage and a climbing-mechanism, none of which can climb to space, even with improvements. Instead both components will need to be made fundamentally different.

Most serious designs I've seen use energy from an external source, because if you are carrying your own energy on the climber, then you use most of your power to lift the energy-storage. (sorta like rockets are mostly lifting rocket-fuel) Ideas include powerful lasers shining on the thing from below, being converted to electricity by efficient photocells. (cells tuned to a single frequency like laser can be more efficient than full-spectrum cells) The laser will get weaker as the climber gains heigth, but so will gravity and thus the required energy.

For the actual climbing a non-contact method would be preferable, perhaps something involving magnetism. (essentially a vertical maglev) The trick is to manage that without making the ribbon itself much heavier. (and thus more expensive)

Ah, but now the US has to hurry up and get back to the moon so they can plant the evidence of the Apollo landings... Because if the Chinese get there first they will destroy the evidence of the Apollo landings.
Doesn't thinking like that make your head hurt?

Errr, they'd be halfway there? Not yet in space, nor really much of anywhere important. They'd just be..halfway. Building the ascender for a space elevator should not be the difficult part of this endeavour. It's comparable to a bunch of automotive engineers running into great technical conunundrums while trying to figure out how to make a wheel.

Actually half of the proposed distance would be well beyond the accepted barrier of space. Problem is half doesn't work becuase in order for the tensions and the orbit to be correct, the theory is that the counter-balance satellite would be somewhere near 60,000 miles from the surface of the Earth. 30,000 miles is well beyond the accepted barrier of space at 62 miles, in fact it is nearly 484 times the height of the accepted barrier of space.

then try this link [www.isr.us] for those of you who don't know what a "space elevator" is (and insist on hanging around here). It is a faq on a study done on the concept. More info is also on the site.

No: if it was just the cable, it would need to be twice the lenght of geo-sync orbit. The thing is, there will be a massive satellite at the end. Presumably, in fact, the satellite could be designed to be a launching-off point for interplanetary flight (via building the ship in orbit, instead of having to lift it off the surface). Its pretty easy to show that with a sufficiently massive satellite, the cable can be basically an arbitrary length (or more accurately, an arbitrary length longer than geo-sync orbit).

I would agree if the cable was the same mass the entire length and did not have a large mass tied on the end. I would think a length greater than geosyncronous but less than 2 X geosyncronous would work if the weight force above was enough to counter the gravity force on the section below geosyncronous. The force would have to include not just the ribbon, but the elevator and contents. You wouldn't want to yank the weight down to have it land

And the first automobile didn't break the sound barrier either - though we now have an experimental model that has, and consumer-grade vehicles routinely cruise FAR faster than those early manufacturers considered.

Ditto trains. Ditto planes. Ditto ships.

Also: As you get farther up you can go faster for a given horsepower. Once you cross synchronous orbit (or when you go back down) you GAIN energy from going farther, and the limit (if you don't want to keep it as velocity) is how fast you can store or dump it.

Because a space elevator would by nature be very long, and would thus be subjected to a very large torque. The torque on a "60 thousand mile" tall space elevator would be roughly 217,881.7 times greater than the the torque on the Sears Tower ( 1,454 feet tall).

To hold the cable together mostly. The cable needs tensile strength enough to hold the weight of the cable. It's not just the strength of nanotubes that is important: it's their strength to weight ratio.

Progress is progress, I agree. My concern, however offtopic, is the following question: What kind of conductivity is a 60,000mi carbon nanotube antenna going to have? No one seems to know for certain what kind of geomagnetic effect such a large antenna would have during solar storms. Worst case, catastrophic climate change...Best case, dazzling aurora.

The google cache posted in the parent is bogus. It's a goatse link and actually managed to hang firefox. It wasn't able to render the full image before hanging, but anyhow, this looks like a trend. Fuck off, we don't need people like that here. We'll always have them, but fuck off anyway.